# CIE AS & A Level Physics : 8.4 The diffraction grating – Exam style question – Paper 1

### Question

Light of a single wavelength is incident normally on a diffraction grating.

The resulting diffraction pattern is displayed on a screen.

Which change makes the first orders of intensity maxima further apart from each other on the screen?

A    placing the screen closer to the diffraction grating

B    using a diffraction grating with less separation between adjacent slits

C    using a diffraction grating with more slits but keeping the same separation between adjacent slits

D    using light with a shorter wavelength

Ans:

### Question

Green light is incident normally on a diffraction grating and forms a diffraction pattern on a distant screen. Which change, on its own, would decrease the separation of the diffraction maxima on the  screen?
A Increase the distance between the screen and the diffraction grating.
B Replace the diffraction grating with a grating that has a smaller separation between the slits.
C Replace the diffraction grating with a grating that has fewer slits per unit length.
D Replace the green light with red light

Ans :

### Question

Light of a single unknown wavelength and blue light of a single wavelength are both incident
normally on a diffraction grating. Two diffraction patterns are produced, one for each wavelength
of light.
The third-order maximum for the blue light occurs at the same angle as the second-order
maximum for the light of unknown wavelength. The wavelength of the blue light is 480 nm.
What is the unknown wavelength?

A  320 nm

B  720 nm

960 nm

D  1440 nm

Ans:

### Question

A parallel beam of white light passes through a diffraction grating. Orange light of wavelength
600 nm in the fourth-order diffraction maximum coincides with blue light in the fifth-order
diffraction maximum.
What is the wavelength of the blue light?
A 450 nm      B 480 nm      C 500 nm      D 750 nm

### Question

Light of wavelength λ is incident normally on a diffraction grating, as shown. The angle between the two second-order maxima is ϕ.
Which expression gives the spacing of the lines on the diffraction grating?
A  $$\frac{\lambda }{sin\theta }$$        B  $$\frac{\lambda }{\left ( sin\theta /2 \right )}$$      C  $$\frac{2\lambda }{sin\theta }$$      D  $$\frac{2\lambda }{sin\left ( \theta /2 \right )}$$